Plunger pad for container closing machines



n J. A. WOERZ 2,350,438

' PLUNGER PAD FOR CONTAINER CLOSING MACHINES Filed Oct. 2, 1940 2 Sheets-Sheet 1 1/ June 6,1944. I J. A. WOERZ 2 PAD FOR: CONTAINER CLOSING MACHINES Fiied Oct. 2, 1940 2 Sheets-Sheet 2 Patented June 6, 1944 PLUNGER PAD FOR CONTAINER CLOSING MACHINES John A. Woerz, Philadelphia, Pa., assignor to Crown Can Company, Philadelphia, Pa., a corporation of Pennsylvania Application October 2, 1941), Serial No. 359,428

3 Claims. (Cl. 226-71) The present invention relates to plunger pads for use in connection with machines for applying ends to cans or other containers filled with food or similar products, particularly, for use with machines such as the present-day commercial sanitary can double-seaming machines.

In the packaging of such products as foods in cans, it is customary, before applying the closure end or top to the can, to press a circular plate carried by a suitable operating arm into the open end of the can, said plate being known as a plunger pad.

In connection with the packaging of food products, the plunger pad may be employed to regulate the quantity of the product in the can, for instance, in order to prevent over-filling. If too much food has been placed in a can, during the filling operation, the plunger pad serves to displace this excess food from the can, thereby insuring the correct volume fill.

In the packaging of solid food products in cans, such as tomatoes, and mixtures of solids and liquids such as string beans in brine, the plunger pad is used to compress the products completely into the can before the top is applied thereto for attachment by the conventional double-seaming or similar operation. When filling cans with such products as tomatoes and beans, the ends or portions thereof often extend beyond the open end of the can after the filling operation, and it is necessary to tightly pack these products entirely into the can in order to be able to properly apply the top or closure thereto.

In the past, it has been the custom to employ a metal plunger pad for the above purposes, often one made of ferrous composition. In the canning of many foods, the product is surrounded in the can by a brine. I have noted that, because the can is made of tin, an action similar to that of a battery is set up when an iron or other metal pad is pressed into the filled can, particularly when the'contents thereof include a brine which may act as an electrolyte. Due to this battery or similar action, and depending on the direction of flow of the resulting induced electric currents, some slight amount of either the tin from the can or the metal from the plunger pad may go into the solution in the contents of the can. This results in a contamination of the product, with possible impairment of its palatability, color and odor.

In place of the conventional metal plunger pads, I have successfully employed such a, pad made of a non-metallic material, and preferably a transparent non-metallic material. I have discovered that a plunger pad made of one of the new well-known plastics, such as a synthetic plastic known as methyl methacrylate polymer operates satisfactorily while eliminating the disadvantages of the metal pad, as discussed above.

While I have employed a plunger pad made of the plastic mentioned above, it will be obvious that other suitable non-metallic materials may also be successfully employed. As will be hereinafter apparent, a transparent plastic affords outstanding operatin advantages, and is preferred. Among the other non-metallic materials contemplated for the plunger pad are pyroxylin, transparent Bakelite, and other transparent synthetic resins.

As far as I know, no one has heretofore used a transparent plunger pad for compressing food into a filled container prior to attaching the closure end thereto, or fOr the purpose of regulating the fill of the can. In the use of metallic plunger pads, particularly when operating in cans containing solid materials such as vegetables, the latter have been crushed and bruised by the pad. In view of the fact that present-day opaque plunger pads completely cover the open ends of the cans being operated upon, so that the attendant cannot view the contents thereof at the time when the pad is inserted into the open end of the can, bruising of the product in some cases cannot be avoided. By using a transparent plunger pad, I have found that this defect can be avoided, for with the contents of the can at all times in view of the attendant, he can easily exercise the necessary control over the operation of the plunger pad to avoid crushing the contents thereof, while at the same time applying the necessary pressure to obtain the desired fill.

The advantages afforded by the use of a transparent plunger pad are of great importance, and will be discussed in more detail hereinafter in connection with the description of a seaming machine and various types of plunger pads which may be used in association therewith.

In the drawings, which are only intended to be diagrammatic and illustrative:

Figure 1 is a diagrammatic plan view of the path of cans in their travel toward the seaming station of a, representative machine, illustrating the position of the plunger pad table or 'turret;

Figure 2 is a side elevational View of such a machine, partly in section along line 2-2 of Figure 1, showing the general manner of operation of one type of plunger pad operating mechanism; and

Figures 3 through 7 illustrate various form of the plunger pad of the present invention, emphasizing the advantages of the transparency thereof, particularly the control of the operation of the plunger pad which the attendant is able to exercise.

In Figures l and 2 a seaming station table is shown at T, and it is to this table or lifter head that the filledcans are finally brought, and they are there elevated to a seaming head S having the well-known seaming rollers which secure the closure ends to the can in the manner Well-known in the art. By suitable and well-known means as shown, closure ends are applied to the cans before the platform T elevates them to seaming position. While only one seaming head is indicated in the drawings, which are stated to be illustrative only, it will be understood that the present invention may be used in connection with any design of seaming machine, especially the improved types having multiple seaming heads.

Referring to Figure 1, the cans may pass clockwise over a conventional feed table [0, and from this table they are urged onto a can spacing table l2 by a deflector I4. After being properly positioned with respect to one another by the spacing shoes IS, the cans encounter a guide rail l8 which delivers them successively between the arms of a rotating star wheel which in turn delivers the cans onto the main part of the table 22 of the machine. Suitable side guides or rails are provided to guide the cans while they are being moved by the star wheel;

It is while the cans are being moved by the arms of the star wheel 20 that the plunger pads operate on the contents thereof, in the manner hereinafter described and well-known in the. art. The star wheel 20 is mounted on a vertical hollow rotating shaft 23 which projects downwardly therefrom and carries near the lower end thereof agear wheel 24. This gear wheel is one of a train of gears by which the fed table I9 and the spacing table l2 are rotated. Slidably keyed upon the upper end of the hollow shaft 23 is a plunger pad carrier 26. This carrier is provided with a plurality of circularly spaced Vertical bearings 21 corresponding in number with the arms of the star wheel 20 and in each bearing there is mounted a vertically sliding plunger pad rod 28. Each of the rods 28 is provided at its lower end with a plunger pad P which is operated to partially enter the open ends of the cans and press the contents therein or to displace the surplus contents therefrom in the case of liquids, as the cans are conveyed on the table beneath the plunger pads by the star wheel 20.

The rods 28 are provided adjacent their upper ends with cam rollers. 30 which engage a, stationary cam track 3| secured to the upper end of a non-rotating shaft 32 positioned within the hollow shaft 23.

The lower part 33 of the cam track 3| is at the point where the operation of the plunger pad in pressing the contents into the cans is to be effected and the high part of the cam track is at a diametrically opposed point, as indicated in Figure 2. As the plunger pad carrier 26 rotates with the star wheel, the cam rollers 30 carried thereby travel about within the stationary cam track 3|. When the rollers enter the low part 33 of the track, they cause the rods 28 and the plunger pads P to successively descend, thus pressing the contents into the cans at the proper time. This operation is well-known in the art, and has been heretofore accomplished to insure that the cans may be uniformly filled, and the contents pressed therein, so that closure discs may be properly applied to the ends of the cans preparatory to the double-seaming operation. As the cans continue on their course under the action of the star wheel 20, the cam rollers 30 enter the high part of the cam track 3|. thus removing the plunger pads from engagement with the open cans. The cans are thus permitted to be further moved on the table 22 until they are received by a suitable conveyor such as a chain conveyor C having suitable teeth to engage in the rear of the cans and carry them to the double-seaming station S.

The shaft 32 extends downwardly through the hollow shaft 23 and is supported for vertical adjustment by a hand wheel collar 35, which is supported on a bracket 36 attached to the frame F of the machine. By rotating the hand wheel 35, the attendant is able to exercise control over the operation of the plunger pads, for by elevating and depressing the shaft 32, the vertical position of the plunger pad rods 28 can be regulated and thus the amplitude of the movement of the plunger pads into the cans can be controlled. The shaft 32 is held against rotation but it is capable of vertical adjustment in the fitting 36 by means of a suitable key-way.

It will be understood that the apparatus described above is illustrative only, and the invention is applicable to other similar types of apparatus employed in the art.

In the operation of the conventional machines of the above general type, wherein opaque plunger pads are employed it hasbeen the custom to observe the condition of the contents of the cans as they pass from the plunger pad operating station toward the platform T of the double-seamer, or in the case of a multiple head seamer, toward the turret on which the cans are carried during the seaming operation. This observation is made to determine if the proper degree of pressure has been exerted by the plunger pads to pack the product in the cans to the desired degree.

If the product has not been compressed sufficiently into the interior of the can, itis impossible to properly position the can closure or lid on the open end of the can, and the effectiveness of the seaming operationwill thereby be impaired, with the result that a tight and permanent seal between the flange of the can body and the flange of the closure lid may not be effected. Improper sealing may cause spoilage of the contents of the can which may not become evident until the product is on the market. On the other hand, if the product is compressed too tightly into the can, there is danger of damage to the particular articles being packed, especially in the case of such food products as solid fruits and vegetables. It will be understood that it is desirable to package such solid prod- ,ucts in a manner most closely approximating the natural shape, appearance and condition of the particular fruit or vegetable.

As the plunger pad entirely covers the open end of the can during the time when the product is being compressed, it will be obvious that when an opaque plunger pad is used, the attendant cannot observe the degree of compression of the product until after the cans have left the plunger pad operating station. Therefore, anydefective adjustment of the vertical movement of the plunger pads cannot be corrected -'until after a number of cans have perhaps been improperly packed. .In the use of plunger pads of the present invention, made, of transparent material, their operation can be closely and continuously observed, and if an improper'degree of compression is being exerted, the defect canbe immediately corrected by adjusting the hand wheel 35. It will be understood that the hand wheel 35, or the equivalent thereof, may be operated from any convenient point in order to constantly maintain proper movement of the plunger pads. As modern canning machinery operates at high speeds, it is highly desirable to correct any errors in packing products as quickly as possible, in order to reduce the number of improperly packed cans in any given bulk or run.

Figure 3 illustrates the manner in which high grade or so-called fancy pack tomatoes are arranged in a can prior to the final sealing operation. Such fancy products are usually arranged by hand in the cans as close to one another as possible, in order to use the full volume of the can. In Figure 3 it will be observed that the tomatoes at the top of the can protrude to some extent above the upper open edge thereof. It will be obvious from this figure that it would be impossible to apply a closure lid to the open end of a can filled as illustrated without first compressing the tomatoes downwardly into the can.

While the tomatoes appear to be closely packed there are a considerable number of air spaces or pockets between adjacent tomatoes, and when the plunger pad is operated to compress the tomatoes into the can, in the manner previously described,

these air spaces are substantially eliminated. As

stated before, the amplitude of movement of the plunger pad into the cans should be accurately regulated so that the contents are completely enclosed in the can to permit the closure lid to be applied thereto. However, it is obvious that if too great a degree of pressure is exerted on this product, the tomatoes will be so tightly packed together that they will lose their natural shape and appearance. By using the transparent plunger pad of the present invention, the application of the proper degree of pressure is insured. A preferred form of the plunger pad for the particular use illustrated, is disclosed in Figure 3. This pad comprises a circular disc 30 of diameter slightly greater than the diameter of the can so that the outer and lower surface of said disc lies over and may engage the outwardly turned flange of the can when the plunger pad is moved downwardly toward the same. The disc 42 is provided with a concentrically located conical depending pressure portion 42, having a fiat lower face which engages the product and forces it downwardly into the can. Centrally located on the top face of the disc 40, there is a threaded boss 44, by which the plunger pad is secured to the reciprocating rod 28, as by means of a set screw. By reason of the deslgn of the depending portion 42 of the plunger pad, the contents of the can may be easily compressed downwardly or inwardly thereof. In case there is any liquid in the can, excess quantities thereof may be displaced from the can by the entry of the depending portion 42. I The above discussion was concerned principally with the packaging of comparatively spherical vegetables or fruits such as tomatoes, but it will be understood that a similar problem is encountered in the canning of other vegetables such as whole string beans and whole kernel corn. Whole string beans are usually placed in the container I by hand after which the can is filled with a brine solution' When the containers are thus filled with beans and brine, there still remains in the can a, considerable number of relatively small open spaces resulting from entrapped air. In the art of food packaging, it is customary to pass the filled cans through a hot water or steam exhausting chamber prior to the application of the closure end thereto. During this time, there is expansion and partial cooking of the product, such as beans, which may cause some disarrangement of the product so that it may protrude above the open end of the can to an undesirable extent. In order to eliminate as much as possible of this undesirable entrapped air and further to force the vegetable entirely within the confines of the can, it is the custom to subject the product to the action of the plunger pads.

In packaging some vegetables, such as string beans, considerable difliculty is experienced in sealing the closure lid to the can because of portions of the product which may protrude outwardly over the open flanged edge of the can. Plunger pads of different shapes and contours are designed to effectively force various types of vegetables into the cans, as described above, preparatory to the double-seaming operation. If the plunger pads are transparent as in the present invention, it can be readily and quickly determined whether the proper pad is being used for the particular food or vegetable being packaged. Such convenient observation of the effectiveness of this operation is impossible when opaque plunger pads,'such as the present-day metal plunger pads, are used.

In Figure 4, a plunger pad substantially identical in bottom contour to that of Figure 3 is shown, but having a top surface which is dished out as at 46. Like in Figure 3, this pad is shown positioned in spaced relation above the open end of the can, and it will be noted that the beans which fill the can extend out over the open edge thereof as previously described. This pad has a fiat circular bottom edge area 48 which almost engages the lip of the can when the pad reaches the point of its maximum downward movement. Inwardly of the circular area 48 the pad has a downwardly depending conical portion which progressively decreases the opening from the can as the plunger pad moves into the same. At the termination of the downward movement of the pad, any portions of the beans extending above the lip of the can will be cut off. This type of pad may not only be used to compress tomatoes and the like into a can, like the embodiment of Figure 3, but may be also used effectively in pulling the ends of string beans and the like lying over the lip of the container, entirely into the interior thereof, so that the container closure lid can be properly applied.

In Figure 5, another design of plunger pad is shown, which may be used in connection with the canning of whole grain corn and similar materials. Whole grain corn is usually covered with brine at the time of the filling operation, yet there remains a considerable number of small air spaces throughout the body of the corn after filling, as described in connection with the packaging of string beans. It is desirable to eliminate this air from the can before the closure end is permanently sealed thereto. In actual canning operations, the cans are usually filled with whole grain corn in such manner that the top portion of the bulk thereof extends somewhat above the lip of the can, as shown in Figure 5. When the entrapped air is forced from the can by operation of the plunger pad, its place is taken by the compression of the total bulk of corn entirely into the confines of the can.

The plunger pad as shown in Figure 5 is of plain disc form and of diameter substantially equal to the interior diameter of the can, so'that the pad can enter the open end of thecan to adequately compress the corn therein. .A plurality of vertical openings 50 are provided through this plunger pad so that the liquid brine in the can mayrise through the openings aspressure is applied to force the corn into the can, and these openings will permit relief of the air expelled from the can. Another design of plunger pad is shown in Figure 6. Thispad has a plain top face similar to that of Figure 3, but on the bottom face thereof is a downwardly depending circular ridge 52 which is designed to lie within the open end of the can in spaced relation with the inner Wall thereof. Th outer face of this ridge is tapered in a manner somewhat similar to the depending portion shown in Figure 4, except that the taper may be somewhat more acute. As in the case of the embodiment of Figure 4, this depending ridge serves to draw such products as string beans, which may extend over the lip of the can, entirely intothe interior thereof. This plunger pad also has a fiat bottom area at its perimeter which extends out over the lip of the can and may ongage the same to finally cut offany extending portions of the vegetables.

Figure 7 illustrates still another design of the plunger pad, similar to that of Figure 6 except that the depending ridge 54 tapers outwardly to a diameter greater than that of the inside of the can, and the bottom fiat circular area adjacent the perimeterof the pad as in the embodiment of Figure 6 is eliminated. The ridge 54 is preferably somewhat deeper, than the ridge 52 of the embodiment of Figure 6. In the operation of the pad of Figure 7, the cutting off of the extending ends of the vegetables may be more positive, as the conical surface 56 of the pad will sever such vegetables as beans more cleanly than may be the case when using the embodiment of Figure 6. It may at least be said that a pad designed as in Figure 7 will operate more satisfactorily with some vegetables or materials than will the designs of the other figures, but the latter may be more effective in the particular uses for which they are designed.

For instance, it has been found that a plunger pad of the type shown in Figure '7 operates more effectively in connection with kraut, which has a tendency to swell outwardly beyond the lip of the can. The particular design of Figure 7 has been found to be effective in pulling the shredded strands of kraut into the can and in cutting the extending ends therefrom in a manner somewhat superior to that .of the other embodiments.

It will therefore be apparent that different products such as different fruits and vegetables, present different problems in canning, and in order to operate most effectively on a wide variety of products, plunger pads of different designs are required. manner of operation of these various pads may differ somewhat, in order to secure the best results. That is, when operating on some vegetables, one form of pad may be used, while another pad may be used with other vegetables or fruits. A particular design of plunger pa may operate mor effectively whenthe amplitude of the stroke of the pad into the can is increased or reduced as compared with the stroke when It will be further evident that the using other forms of the pad. Some pad de- 7 signs may require a greater or lesser stroke than others. In order that the most effective action may be had from a particular design of the plunger pad, or when operating upon a particular product, it is highly desirabl that the attendant closely observe its operation as it is actually compressing the material into the can. Actual visualobservation of the pad as it enters the can will enable the attendant to get the-best results when working with a particular product, by selecting the proper pad and by accurately adjusting its stroke, as previously described.

Such close observation and adjustment is not possible when using present-day opaque plunger pads, such as the conventional metal plunger pad, but in the use of my improved transparent pads, as illustrated in Figures 3 through 7, the operation of any design when used with any particular product may be closely and continuously observed and its operation accurately regulated.

Plunger pads of plastic material similar to that discussed herein present a very smooth surface substantially free from irregularities such as exist on the surfaces of the conventional metal pads. Plunger pads of plastic material which I have developed, by reason of their smooth surfaces, cause less damage to fruits, vegetables and the like upon engaging the same, and, furthermore, my plunger pads of plastic material may be more easily kept clean. By reason of the fact that my pads are transparent, any uncleanliness may be immediately observed and remedied.

The present-day plunger pads of metal have been found to be subject to considerable corrosion, particularly when used in connection with food products as mentioned above, which are canned in brine, or which are acid in nature, such as fruits. It is well-known that this brine as well as some food products have a tendency to form a compound with the metal of the pads with resulting surface corrosion. In the case of apples, for instance, the malic acid present is very corrosive. When plunger pads of ferrous composition are employed in connection with such foods as sweet potatoes, they have a tendency to cause a dark discoloration on the surface of the product due to the formation of iron tannate. The market value of a product is obviously impaired when the consumer finds surface discoloration upon opening the can. In certain cases, corrosion of a metal plunger pad has been known to impart a metallic taste to the product.

Some food products such as sweet potatoes, when vacuum packed, tend to adhere to the conventional metal plunger pads, and when the latter are elevated from the open ends of the cans, in some instances, portions of the food product are carried upwardly with the pads, thus destroying the uniformity of the fill. This tendency of certain foods to adhere to the plunger pad is entirely eliminated when'using a plunger pad of plastic material as in the case of the present application. The entire plunger pad may not be formed of the plastic material, but the same may serve as a covering perhaps for a metal disc or the like. Furthermore, a metal disc might be covered with rubber, lacquer, cement, certain oil coatings, synthetic resins and the like, in order to reduce corrosion and eliminate such difficulties as adhesion of the food product to the plunger pad. However, I prefer to make the plunger pad substantially wholly of the plastic material, and pronounced advantages are afforded byusing a transparent plastic material, as discussed in detail above.

I claim:

1. For use with machinery for filling and applying closure ends to containers, a plunger pad to be arranged for downward movement over and into the open end of a container to force the contents thereof completely within the confines of the container, preparatory to the application of a closure end thereto, said pad being made of a tough, slightly flexible, non-chipping, heat resistant, transparent synthetic resin, plastic material whereby its effect on the contents of a particular container in compacting the contents therein may be continuously observed by visual inspection through the body of the pad.

2. For use with machinery for filling and applying closure ends to containers, a plunger pad to be arranged for movement toward the open ends of containers to compact the contents thereof and regulate the fill of the container, preparatory to the application 01 a closure end thereto,

said pad. being made or transparent methyl methacrylate polymer, whereby the compacting efiect of the pad upon the contents of the containers may be ascertained by visual observation through the pad and the operation of the filling machine adjusted accordingly.

3. For use with machinery for filling and applyingclosure ends to containers, a plunger pad adapted for movement toward the open end of a container to compact the contents thereof and to regulate the fill of the container, preparatory to the application of a closure end thereto, said pad consisting of a body of tough, slightly flexible, non-chipping, transparent, synthetic resin material which will not be corroded by the contents of the container or impair the color or taste of said contents when brought into contact therewith, and which makes possible visual inspection of the contents of the container through the body of the pad during the compacting operation.

JOHN A. WOERZ. 

